Tuberculosis (TB)

Summary


Improving the detection and treatment of TB cases

4. A total of 201 countries reported to WHO on their strategies for TB control, and on TB case notifications and/or treatment outcomes.

5. Using trends in case notifications to update estimates of incidence, we calculate that there were 8.8 million new cases of TB in 2002, of which 3.9 million were smear-positive. The global incidence rate of TB (per capita) was growing at approximately 1.1% per year, and the number of cases at 2.4% per year. The growth in case notifications has been much faster in African countries with high HIV prevalence, and in eastern Europe (mainly the former Soviet Union), but growth has been decelerating in both these regions since the mid 1990s.

6. The number of countries implementing the DOTS strategy increased by 25 during 2002, bringing the total to 180 (out of 210). NTPs reported that, by the end of 2002, 69% of the world's population lived in countries, or parts of countries, covered by DOTS. DOTS programmes notified 3.0 million new TB cases, of which 1.4 million were smear-positive. A total of 13.3 million TB patients, and 6.8 million smear-positive patients, were treated in DOTS programmes between 1995 and 2002.

7. The 1.4 million smear-positive cases notified by DOTS programmes in 2002 represent 37% of the estimated incidence, just over half way to the 70% target. The increment in smear-positive cases notified under DOTS between 2001 and 2002 (214 656) was greater than the average from 1995--2000 (134 157). The acceleration in notifications was more pronounced for all TB cases, which increased by 610 228 between 2001 and 2002, as compared with the average annual increment of 269 268 in the interval 1995--2000. Nonetheless, to reach 70% case detection by 2005, an additional 1.04 million TB cases, and an additional 433 000 smear-positive cases, must be found in each of the years 2003--5.

8. While the number of TB cases reported by DOTS programmes appears to have been accelerating since 2000, the total number of TB cases reported to WHO increased very little over the period 1995--2002 (average detection rate 46%). The number of smear-positive cases reported from all sources has been increasing (44% detection rate in 2002), but much more slowly than the increases reported under DOTS. If these trends continue, all cases notified to WHO by 2005 will be notified by DOTS programmes.

9. Twenty-eight percent of the additional smear-positive cases reported under DOTS in 2002 were found in India. There were smaller but apparently significant improvements in case detection in South Africa (contributing 12% of the total increase), Indonesia (10%), Pakistan (4%), Bangladesh (3%), and the Philippines (3%). These 6 countries together accounted for over 60% of the additional cases detected in 2002.

10. As DOTS programmes have expanded geographically, the smear-positive case detection rate within DOTS areas has remained roughly constant since 1996 (average 49%), though there are signs of a slow increase in the HBCs, led by India, Indonesia, Bangladesh, and the Philippines.

11. Treatment success under DOTS for the 2001 cohort was 82% on average, the same as for the 2000 cohort. As in previous years, treatment success was substantially below average in the WHO African Region (71%) and in eastern Europe (70%). Low treatment success in these two regions can be attributed, in part, to the complications of HIV co-infection and drug resistance, respectively. Equally important, though, is the failure of NTPs to monitor the outcome of treatment for all patients.

12. Based on case reports and WHO estimates, 18 countries had reached the targets for case detection and cure by the end of 2002. However, Viet Nam was the only high-burden country among them.

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